1. Technical Field
The present invention relates to an adaptive safety restraint system, and more particularly to an airbag module employing a deflagration venting system for adaptively changing the level of venting provided during airbag inflation.
2. Discussion
The use of airbag systems for protecting a vehicle occupant in crash situations is well known within the prior art. To promote occupant safety in a variety of crash scenarios, vehicles are being outfitted with different types of airbag and safety restraint systems. For example, a vehicle may include airbags positioned in front of the seat occupant as well as airbags positioned along the door side of the seat occupant. The vehicle may also include inflatable knee bolsters for providing additional protection to the seat occupant, and seat belt pretensioners for taking up any slack in a properly fastened seat belt.
These first generation airbag and safety restraint systems are typically driven by individual inflators having a stored energy device which is activated by the vehicle's crash detection system. Typically, actuation of the inflator generates a predetermined output, based on the magnitude of gas or propellant discharge, for driving its associated airbag or safety restraint device. However, a vehicular collision producing less impact force does not require the same amount of airbag inflation to absorb the energy transferred to the seat occupant as a vehicular collision producing greater impact force. Accordingly, this desire for adaptive airbag systems has prompted investigation into regulating the output of an airbag inflator, and thus the deployment force of the airbag.
One method for regulating the output of the airbag inflator is through the use of a multi-level inflator having two or more separate stored energy devices. Typically, the multi-level inflator includes a first stored energy device associated with a smaller propellant chamber and a second stored energy device associated with a larger propellant chamber, each of which can be independently activated. In response to a relatively minor crash, only the first stored energy device is activated for inflating the airbag. Likewise, in a more severe crash, only the second stored energy device is activated. However, in a high severity crash, both stored energy devices are simultaneously activated for providing maximum inflator output. This same multi-level inflator approach can alternatively be used for regulating inflator output in response to the size of the vehicle occupant, if used in conjunction with the appropriate occupant detection sensors. However, multi-level inflators are expensive to produce because two separate inflation gas sources must be integrated into a single unit. Moreover, even if only one of the chambers is discharged, the entire inflator must still be replaced.